The present invention relates to a semiconductor laser diode employed in an optical-information processing system counter and laser pointer for optical communication, and more particularly, to a method of manufacturing a ridge-structured semiconductor laser diode formed using self alignment, to have a small luminescence area for high density and high-speed information processing in optical communication.
FIG. 1 is a cross-sectional view of a conventional ridge-structured semiconductor laser diode. Referring to FIG. 1, an n-GaAs buffering layer 2, an n-type first cladding layer 3, a first waveguide layer 4, an activating layer 5 and a second waveguide layer 4 are sequentially stacked on an n-GaAs substrate 1. Sequentially, a p-type second cladding layer 7 having three ridges is stacked thereon. A cap layer 8 is formed respectively on the three ridges.
On the ridged second cladding layer 7 on which cap layer 8 is formed, current cutoff layer 9 is stacked excluding the aperture for current injection placed at the top center of the intermediate ridge. A p-type metal layer 10 is stacked over the resultant structure and is in contact with part of cap layer 8 via the aperture of current cutoff layer 9 in order to transmit injected currents. Meanwhile, an n-type metal layer 11 is deposited on the bottom of substrate 1 and serves as an electrode together with the metal layer 10 which also acts as an electrode.
Now, the method for forming a ridged semiconductor laser diode as above will be discussed.
The n-GaAs buffering layer 2, n-type first cladding layer 3, first waveguide layer 4, activating layer 5, second waveguide layer 6, p-type second cladding layer 7 and cap layer 8 are sequentially stacked on n-GaAs substrate 1.
The stack is etched by photolithography so that two grooves are dug deeply to second cladding layer 7 so as to form three ridges. The current cutoff layer 9 is formed on the overall resultant structure of the ridged stack. Using an appropriate mask, the top surface of the middle ridge is etched via photolithography, to thereby form aperture 12. Metal layer 10 is deposited over the stack on which aperture 12 is formed, completing the device.
However, in the above manufacturing method of the ridge-structured semiconductor laser diode, misalignment is likely to occur due to the photolithography process using a mask for forming aperture 12 for current injection. Further, the narrow ohmic contact area between cap layer 8 and metal layer 10 via aperture 12 generates severe heat in lasing. This is a hindrance to the reliability of the finished device, which is a vital problem to be overcome for optical communication.